Various physical inserts have been proposed in the past in an effort to improve heat conduction and control of liquids within a cooking vessel. Their main object has normally been to prevent burning or scorching of food which normally occurs as a result of contact with the heated bottom surfaces of a cooking vessel.
U.S. Pat. No. 3,908,534 shows an imperforate heat transfer plate designed for use in a frying pan. The plate rests on integral ribs that provide substantial contact with the bottom of the pan, while providing a substantial recess under the top surface of the plate, within which fat from the food can collect.
Numerous patents have disclosed perforated plates arranged about the bottom of a cooking vessel to facilitate steaming or boiling of food while preventing direct contact between the food and the bottom surface of the cooking vessel. Examples are U.S. Pat. Nos. 1,200,741; 1,434,262; 1,627,285; and 3,988,975. They space the cooking food above the heated surface at the bottom of a cooking vessel. By providing an array of perforations about the insert, they tend to distribute the boiling steam developed in the cooking vessel, and thereby help to prevent the food and water from "boiling over" the top of the cooking vessel.
U.S. Pat. No. 877,493 to Dunfee discloses a cooking vessel including a false bottom centrally supported by partitions that divide the space between the false bottom and the bottom wall of a receiving cooking vessel into separate compartments. Steam is directed from these compartments into upright flues about the sides of the cooking vessel, as well as into a central discharge tube having a top check valve. Steam is directed radially inward from the flues and radially outward from the tube to contact food within the cooker for steaming and boiling the food. Condensed water is returned to the bottom compartments through apertures and downwardly extending tubes provided about the false bottom.
U.S. Pat. No. 3,357,342 discloses a specialized insert for increasing the velocity of steam jets directed to a block of frozen food resting on the insert. The insert is stated to be made from ceramic material and has tapered holes formed through it. The patent states that the tapered configuration of the holes creates higher steam velocity than would normally occur with the use of cylindrical holes and much higher velocity than that of steam flowing through holes in a thin body, such as sheet metal, apparently referring to false bottom inserts of the type shown in the previously-described patents.
The present invention involves the utilization of an open metallic grid to conduct heat within a cooking vessel to foods that are being cooked, particularly to those types of foods normally cooked by dry heat in an oven. This includes semi-liquid casserole dishes and baked doughs, such as breads, muffins and biscuits. While such food products can be cooked to an edible state in a frying pan or cooking pot, they will typically cook unevenly, with the bottom of the food mass being overcooked and crusty, if not scorched. One object of this effort was to provide an apparatus and method for cooking such foods which could be accomplished on a flame source or a stove top. The equipment and process described herein particularly apply to camping procedures, where cooking heat is typically available only from a small open fire or from a relatively small, concentrated heat source, such as a portable stove.
U.S. Pat. No. 4,527,538 discloses a portable oven that incorporates a heat transfer grid constructed from the same type of grid structure as disclosed herein. The grid is used to spread and conduct dry heat from a concentrated heat source. The earlier disclosure has no direct application to cooking of food in a covered vessel containing liquid.